The application of distinct lattice spring model to zonal disintegration within deep rock masses

Abstract

Zonal disintegration has been frequently encountered in many tunnelling projects such as deep mining and water tunnels in hydropower stations. The mechanisms of this phenomenon cannot be explained reasonably through conventional mesh-based numerical approaches. Thus, in this study, a dual coupled Micro-Macro Continuum-Discontinuum approach named as Distinct Lattice Spring Model (DLSM) has been applied to investigate the mechanisms of zonal disintegration within deep rock masses. Firstly, the 3D numerical modes are built up, with fixed boundaries being set for far fields and displacement loading being applied along the tunnel axis. This numerical mode is then validated through comparing model simulation with laboratory model tests, where reasonable agreement has been achieved for all cases considered (normal rock mass and layered rock mass with different joint spaces). To cater for real tunnels within various rock masses, tunnels excavated in deep rock masses with different sizes, shapes and material heterogeneities are investigated. Numerical study demonstrates that, the DLSM is capable to reproduce the process of zonal disintegration explicitly, along with which the mechanical responses have been captured reasonably. It shows that, the occurrence of zonal disintegration mainly depends on the material heterogeneities and the in-suite stress level. The fracture patterns formed during zonal disintegration rely on tunnels’ shape, size and the distribution of local weakness in surrounding rock masses.